It is impossible to enjoy idling thoroughly unless one has plenty of work to do. There is no fun in doing nothing when you have nothing to do. Wasting time is merely an occupation then, and a most exhausting one. Idleness, like kisses, to be sweet must be stolen. - Jerome K. Jerome

Monday, July 21, 2008

Men and women show differences in behaviour because their brains are physically distinct organs, new research suggests. Male and female brains appear to be constructed from markedly different genetic blueprints.

The differences in the circuitry that wires them up and the chemicals that transmit messages inside them are so great as to point to the conclusion that there is not just one kind of human brain, but two, according to recent neurological studies.

Men may be from Mars and women may be from Venus, and since the American psychotherapist John Gray wrote his famous book, in 1992, on the idea, it has been a commonplace to think of men and women as being from different planets in terms of their emotional responses.

But until recently, these differences were often explained by the action of adult sex hormones, or by social pressures that encouraged males and females to behave in a certain way.

Increasingly, however, these assumptions are being challenged, according to a review of recent neurological research appearing in this week's New Scientist magazine, and it is becoming clear that the brains of men and women show numerous anatomical differences.

Some of these divergences, the review by Hannah Hoag suggests, could explain a number of mysteries, such as why men and women are prone to different mental health problems, why some drugs work well for one sex but have little effect on the other, and why chronic pain tends to affect women more than men.

One area of research concerns the brain's pain-suppressing mechanisms, and points to the fact that they may be organised differently in men and women. This would explain why women can suffer long-term pain more, and why there can be sex differences in response to opium-derived painkilling drugs. The study notes: "Women get more relief from the opioid painkiller nalbuphine compared to men, whereas in men morphine is more effective and nalbuphine actually increases the pain intensity." It is possible these findings could lead to new painkillers being developed that are tailored to be more effective in women – but that is some way off.

Mental health is another area where real brain differences may offer explanations. Women are diagnosed with depression twice as often as men, and this may be linked to relative levels of the neurotransmitter serotonin. Boys, on the other hand, are more likely than girls to be diagnosed with autism, Tourette's syndrome, dyslexia, attention-deficit disorder and early-onset schizophrenia. The review reports that Margaret McCarthy of the University of Maryland in Baltimore believes that hormone-like substances called prostaglandins, which help masculinise the male brain around the time of birth, may be partly to blame.